#include #include // I cri everytiem std::string add(std::string s1, std::string s2) { // code reused from C++ BigInt Fib sequence std::string t1,t2; char c1=48; int d = s1.length()-s2.length(); for (int i=0; i<(d<0?-d:d); i++) (d<0?s1:s2)="0"+(d<0?s1:s2); for (int i=s1.length()-1; i>=0; i--) { t1 = std::to_string(s1[i]+s2[i]+c1-144); c1 = (t1.length()<2?48:t1[0]); t2 = (t1.length()<2?t1[0]:t1[1])+t2; } return (c1!=48?c1+t2:t2); } std::string soft_multiply(std::string s1, int value) { // a "glue" for BigInt multiplication by repeatedly calling add() std::string sum = "0"; for (int i = 0; i < value; i++) sum = add(sum, s1); return sum; } std::string factorial(int value) { if (value < 0) return ""; switch(value) { case 0: case 1: return "1"; case 5: return "120"; case 15: return "1307674368000"; case 30: return "265252859812191058636308480000000"; case 51: return "1551118753287382280224243016469303211063259720016986112000000000000"; case 99: return "933262154439441526816992388562667004907159682643816214685929638952175999932299156089414639761565182862536979208272237582511852109168640000000000000000000000"; // case 200... 300... // and with every extra case we stray further away from god. default: return soft_multiply(factorial(value-1), value); } } int main() { std::cout << factorial(10) << "\n\n"; std::cout << factorial(50) << "\n\n"; std::cout << factorial(110) << "\n\n"; std::cout << factorial(150) << "\n\n"; }

C++ BigInt Factorial